A conventional method for the manufacture of adipic acid is the air oxidation of cyclohexane to form a mixture of cyclohexanone and cyclohexanol. This mixture is then oxidized with nitric acid to adipic acid.
The preparation of adipic acid is also carried out commercially by the selective hydrogenation of benzene to form cyclohexene, separation of the cyclohexene from the unconverted benzene and the over-hydrogenated cyclohexane by extractive distillation, then hydration of cyclohexene to form cyclohexanol, and the nitric acid oxidation of the cyclohexanol to adipic acid. See for example Kagaku Kogaku (Chemical Technology), vol. 55, No. 5, pp 382-385 (1991); "Technology for Manufacturing Cyclohexanol using Cyclohexene Technique" by Shikazo Senoo and Koji Nakagawa.
British Patent 1,402,480 teaches the preparation of adipic acid by esterification of cyclohexene with adipic acid using an acid catalyst, and then oxidizing the cyclohexyladipates with nitric acid to form adipic acid.
Japanese published patent application 51-36,267 (Published Oct. 7, 1976) discloses that cyclohexyladipates may be formed by the reaction of cyclohexene and adipic acid using an acid catalyst. The published application states: "The cyclohexene used in the present invention may be conventional-grade cyclohexene; the presence of a small amount of inert substances such as cyclohexane and benzene does not present a problem."